Organic semiconductor materials having charge (electron and hole) transport properties have been studied for application to organic photoelectric conversion devices (organic solar cells, optical sensors, and the like) and the like. For example, organic solar cells using fullerene derivatives have been investigated. For example, [6,6]-phenyl C61-butyric acid methyl ester (hereinafter sometimes referred to as [60]-PCBM) has been known as a fullerene derivative (see NON-PATENT DOCUMENT 1).
NON-PATENT DOCUMENT 1: Advanced Functional Materials, Vol. 13, p. 85 (2003)